A Review of the PRPA Zero Net Carbon Portfolio

In the fall of 2017, Catalyst Cooperative was engaged by climate advocates to perform a rapid review of the Platte River Power Authority’s Zero Net Carbon Portfolio Analysis. The PRPA ZNC report was released to the public on December 7th, and we delivered our final report on December 18th.

The ZNC Portfolio Analysis is PRPA’s first attempt to envision moving beyond coal-fired generation. In the scenario explored, by 2030 the utility would generate about 75% of its electricity from carbon free sources. Variable renewables would be firmed using natural gas. The utility would sell excess renewable power into the regional grid, offsetting emissions from a new combined cycle plant.

Despite using conservative projections for the cost of wind, solar, and electricity storage, the resulting portfolio cost only 8% more than the baseline portfolio (in net present value). PRPA’s net CO2 emissions over the study period (2018-2050) would be reduced by more than 75%. In net present value, the emissions mitigation cost was only $3.73/ton of CO2.

In addition to assuming very modest cost declines for renewable energy and battery storage, the scenario explored by PRPA assumed the regional grid would remain dominated by coal-fired generation. This minimizes the zero-carbon electricity they would need to export in order to net out the emissions from their proposed natural gas plant. If the regional grid were to become ~20% less carbon intensive, the studied portfolio would no longer be net zero carbon.

The study did not explore the potential for expanded demand side management and dispatchable demand response. Demand side strategies are highly cost effective ways to balance variable generation and reduce overall generation requirements. The study also does it account for the climate impacts of upstream fugitive methane emissions from natural gas production and distribution systems.

For more details, and pointers to alternative assumptions that could be used for future explorations, please download our full review here: